DependencyPropertyChangedEventArgs.OldValue DependencyPropertyChangedEventArgs.OldValue DependencyPropertyChangedEventArgs.OldValue DependencyPropertyChangedEventArgs.OldValue Property

定義

変更前のプロパティの値を取得します。Gets the value of the property before the change.

public:
 property System::Object ^ OldValue { System::Object ^ get(); };
public object OldValue { get; }
member this.OldValue : obj
Public ReadOnly Property OldValue As Object

プロパティ値

変更前のプロパティの値。The property value before the change.

次の例では、DependencyPropertyChangedEventArgsのコンテキストでクラスをPropertyChangedCallbackイベントも定義するカスタム クラスの特定のプロパティ。The following example uses the DependencyPropertyChangedEventArgs class in the context of a PropertyChangedCallback for a particular property of a custom class that also defines events. コールバックは、以前の結果と、プロパティ システムから新しい値で受け渡されるDependencyPropertyChangedEventArgs、これらのさまざまなイベント引数クラスには、RoutedPropertyChangedEventArgs<T>します。The callback takes the results of old and new values from the property system as communicated by DependencyPropertyChangedEventArgs, and repackages these into a different events arguments class RoutedPropertyChangedEventArgs<T>. 新しい引数は、"ValueChanged"のイベントによって定義され、カスタム クラスによって発生し、データとして使用されます。The new arguments are then used as the data for a "ValueChanged" event defined by and raised by the custom class.

public static readonly DependencyProperty ValueProperty =
    DependencyProperty.Register(
        "Value", typeof(decimal), typeof(NumericUpDown),
        new FrameworkPropertyMetadata(MinValue, new PropertyChangedCallback(OnValueChanged),
                                      new CoerceValueCallback(CoerceValue)));

private static object CoerceValue(DependencyObject element, object value)
{
    decimal newValue = (decimal)value;

    newValue = Math.Max(MinValue, Math.Min(MaxValue, newValue));

    return newValue;
}

private static void OnValueChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
    NumericUpDown control = (NumericUpDown)obj;

    RoutedPropertyChangedEventArgs<decimal> e = new RoutedPropertyChangedEventArgs<decimal>(
        (decimal)args.OldValue, (decimal)args.NewValue, ValueChangedEvent);
    control.OnValueChanged(e);
}
/// <summary>
/// Identifies the ValueChanged routed event.
/// </summary>
public static readonly RoutedEvent ValueChangedEvent = EventManager.RegisterRoutedEvent(
    "ValueChanged", RoutingStrategy.Bubble,
    typeof(RoutedPropertyChangedEventHandler<decimal>), typeof(NumericUpDown));

/// <summary>
/// Occurs when the Value property changes.
/// </summary>
public event RoutedPropertyChangedEventHandler<decimal> ValueChanged
{
    add { AddHandler(ValueChangedEvent, value); }
    remove { RemoveHandler(ValueChangedEvent, value); }
}
/// <summary>
/// Raises the ValueChanged event.
/// </summary>
/// <param name="args">Arguments associated with the ValueChanged event.</param>
protected virtual void OnValueChanged(RoutedPropertyChangedEventArgs<decimal> args)
{
    RaiseEvent(args);
}
Public Shared ReadOnly ValueProperty As DependencyProperty = DependencyProperty.Register("Value", GetType(Decimal), GetType(NumericUpDown), New FrameworkPropertyMetadata(MinValue, New PropertyChangedCallback(AddressOf OnValueChanged), New CoerceValueCallback(AddressOf CoerceValue)))

Private Shared Overloads Function CoerceValue(ByVal element As DependencyObject, ByVal value As Object) As Object
	Dim newValue As Decimal = CDec(value)

	newValue = Math.Max(MinValue, Math.Min(MaxValue, newValue))

	Return newValue
End Function

Private Shared Sub OnValueChanged(ByVal obj As DependencyObject, ByVal args As DependencyPropertyChangedEventArgs)
	Dim control As NumericUpDown = CType(obj, NumericUpDown)

	Dim e As New RoutedPropertyChangedEventArgs(Of Decimal)(CDec(args.OldValue), CDec(args.NewValue), ValueChangedEvent)
	control.OnValueChanged(e)
End Sub
''' <summary>
''' Identifies the ValueChanged routed event.
''' </summary>
Public Shared ReadOnly ValueChangedEvent As RoutedEvent = EventManager.RegisterRoutedEvent("ValueChanged", RoutingStrategy.Bubble, GetType(RoutedPropertyChangedEventHandler(Of Decimal)), GetType(NumericUpDown))

''' <summary>
''' Occurs when the Value property changes.
''' </summary>
Public Custom Event ValueChanged As RoutedPropertyChangedEventHandler(Of Decimal)
	AddHandler(ByVal value As RoutedPropertyChangedEventHandler(Of Decimal))
		MyBase.AddHandler(ValueChangedEvent, value)
	End AddHandler
	RemoveHandler(ByVal value As RoutedPropertyChangedEventHandler(Of Decimal))
		MyBase.RemoveHandler(ValueChangedEvent, value)
	End RemoveHandler
	RaiseEvent(ByVal sender As System.Object, ByVal e As RoutedPropertyChangedEventArgs(Of Decimal))
	End RaiseEvent
End Event
''' <summary>
''' Raises the ValueChanged event.
''' </summary>
''' <param name="args">Arguments associated with the ValueChanged event.</param>
Protected Overridable Sub OnValueChanged(ByVal args As RoutedPropertyChangedEventArgs(Of Decimal))
	MyBase.RaiseEvent(args)
End Sub

注釈

指定された値の型常に報告される依存関係プロパティの型にキャストできる場合があります。The type of the value provided should always be castable to the type of the dependency property being reported.

適用対象